POJ2631 Roads in the North

题面:http://poj.org/problem?id=2631

本题是求树的直径裸题。

Code:
#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<ctime>
using namespace std;
const int MAXN=10005;
struct Node{
    int v,Next,w;
}Edge[MAXN*2];
int head[MAXN],maxDis,Cnt,maxInd;
void Push(int u,int v,int w){
	++Cnt;
    Edge[Cnt].v=v;   
	Edge[Cnt].w=w;
    Edge[Cnt].Next=head[u];
    head[u]=Cnt;
}
void dfs(int now,int fa,int dis){
    if(dis>maxDis){
        maxDis=dis;
        maxInd=now;
    }
    for(int i=head[now];i;i=Edge[i].Next){
        if(Edge[i].v!=fa){
            dfs(Edge[i].v,now,Edge[i].w+dis);
		}
	}
}
int main(){
	int u,v,w;
	while(~scanf("%d%d%d",&u,&v,&w)){
		Push(u,v,w);
		Push(v,u,w);
	}
	dfs(1,0,0);
	dfs(maxInd,0,0);
	printf("%d\n",maxDis);
    return 0;
}